142 Guy |
Jan 9th, 2021 22:29 |
I installed an EPS column unit from a Nissan Versa on my 142. I removed the EPS unit and controller (and most of the steering column) from a wrecked Versa in a pick and pull salvage yard. The all-in cost of the salvaged EPS unit, paying for the machining of support bearings and adapters and welding of parts cost me about $ 600 Cdn - not including my labor / design time.
I picked the Versa EPS for two reasons. The controller has a default assist level that it implements when it loses the speed signal and the clocking of the EPS drive motor was a good fit on my LHD 140. The default assist eliminates the need for a speed signal generator (which would have to be a CAN bus device). The Versa EPS would probably not be a good fit on a RHD car because of interference with the heater (at least on a 140).
My 142 has 185/65 tires and a 14" Moto Lita steering wheel. All of my suspension bits have less than 7,000 km on them including a relatively new upgraded brass idler arm bushing. The car is fine driving around; but, maneuvering, particularly parallel parking is a fight. Although urban driving was definitely acceptable before, whipping around in traffic is much easier and I would never go back.
I have read comments that claim that the installation of EPS can eliminate feel and contribute to wandering at highway speeds, particularly that it eliminates the return to center feel. Perhaps; but, that is because of 1/2 way engineering. I will offer the observation that a lot of the Volvo steering feel is drag. Some EPS units do have a return to center function. My Versa unit does not and I am happy with that because it complicates installation. The real problem is the Volvo steering geometry has very little return to center / self aligning force built in because the OEM caster settings are 0 to 1 deg. You will typically find that modern cars with assist are running caster in the 5 deg range. Volvo did this because minimizing caster minimizes self aligning forces; but also minimizing the force required to steer. With 0 deg caster, add in some power assist which offsets resistance combined with that big OEM steering wheel and you have steering very sensitive to user input at high speed (too much forward gain in Engineering parlance). Increase the caster, a little negative camber is also beneficial and perhaps a slightly smaller steering wheel and you will eliminate the wander issue and have a car that is easy to park and whip around at low speeds. The Versa unit on my car has an input for a CAN bus based speed signal which I have wired out; but, so far I have not been particularly motivated to fiddle with that because the assist level is low enough at highway speeds that with my slightly revised geometry (I am experimenting with about 1.5 deg caster) I am not wandering all over the place at highway speeds.
The final benefit that I got when I did this is that when I lifted the steering column out of the Versa I took the lower shaft with its U joints and splined collapsible shaft. This allowed me to eliminate the rubber bushing mounted break away shaft on the 140. Even with fresh rubber bushings on the break away shaft that contraption contributes a lot of flex in the steering column. The revised lower steering shaft with its U joints will facilitate a possible switch to a steering rack in the future if the steering box ever gives up.
When I started out on the conversion, I sourced a spare steering column and mounting bracket from another 140 owner I know who had a parts car and who donated the parts to me because he was also interested in the conversion. I did this to allow me to go back to OEM in case the conversion turned out to be a bad idea. After two years, safe to say that I am not going backwards and returned the parts to the original owner marked up so that he could do a similar conversion.
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